Transcript No Slide Title

CSC 405 Lab 1 - Building a Simple Combinatorial Circuit
In this laboratory exercise you will learn about the layout of some small-scale integrated circuits (SSI ICs), lightemitting diodes (LEDs), and the electronic experimenter’s socket board (breadboard) as you design and build a
simple combinational circuit.
1. First lets get familiar with the breadboard. The bread board has many strips of metal (copper usually)
which run underneath the board. The metal strips are laid out as shown below.
Bottom View
Top View
These strips connect the holes on the top of the board. This makes it easy to connect components
together to build circuits. To use the bread board, the legs of components are placed in the holes (the
sockets). The holes are made so that they will hold the component in place. Each hole is connected to
one of the metal strips running underneath the board.
Each wire forms a node. A node is a point in a circuit where two components are connected.
Connections between different components are formed by putting their legs in a common node. On the
bread board, a node is the row of holes that are connected by the strip of metal underneath.
The long top and bottom row of holes are usually used for power supply connections. On some boards
these long strips run the entire length of the board. On others they only run halfway.
The rest of the circuit is built by placing components and connecting them together with jumper wires.
For chips with many legs (ICs), place them in the middle of the board so that half of the legs are on one
side of the middle line and half are on the other side.
2. Now we will examine the light-emitting diode (LED). The important thing to remember about diodes
(including LEDs) is that current can only flow in one direction. When the proper voltage is applied to the
leads of the LED it will glow. To make an LED work, you need a voltage supply and a resistor. If you try
to use an LED without a resistor, you will probably burn out the LED. The LED has very little resistance
so large amounts of current will try to flow through it unless you limit the current with a resistor. As a test
we will make our LED light up using the simple circuit below.
Look closely at the leads of the
LED. The longer lead is the
one that must be connected to
the positive side of the power
source.
3. Next we will identify the integrated circuits (ICs) used in this exercise. We will be using
TTL (transistor-transistor logic) ICs containing NOT gates (7406), AND gates (7408) and OR
gates (7432). Your particular ICs may include other letters or numbers within the 7400 series
number, such as 74LS06 or 74F32.
7408
7432
7406
Looking down at the top of an IC, find the end with the notch (or possibly a small dot) and
place this end to the left. The gates inside the IC are connected to the IC pins (legs) as
shown in the diagrams above. In addition to the gate connections each IC will have
connections for power (VCC) and ground (GND).
If you are unfamiliar with the proper use of the breadboard or how the ICs should be placed
on the breadboard please ask the lab instructor for help.
4. Insert each of the ICs into the breadboard leaving at least 5 columns of holes between ICs.
Choose one of the long rows at the top as your +5V line and one of the long rows on the
bottom as your ground line. Connect each VCC pin to the +5V line and each GND pin to the
ground line.
5. Test one of the gates in each IC by connecting the gate output to the positive lead of the
LED circuit and then connecting +5V or ground to the gate inputs. Verify the functions of the
NOT, OR and AND by recording your observations in the tables below.
A B
A AND B
A
NOT A
A B
0 0
0
0 0
0 1
1
0 1
1 0
1 0
1 1
1 1
+5V or Gnd
+5V or Gnd
Connect gate inputs to +5 volts or
to the ground line.
+5 V = true
Gnd = false
330 Ohms
A OR B
6. Simplify the following Boolean expression:
F(A,B,C) = ABC’ + AB’ + A’BC + ABC + A’B’C’
A
BC
00
01
11
10
0
F(A,B,C) =
1
7. Draw the circuit diagram for the simplified Boolean expression.
A
B
C
8. Implement your circuit using the necessary ICs and test it to verify your design.
0 0 0
Did your circuit output match the function for
F(A,B,C) for all values of A, B and C?
____________
0 0 1
Discuss your results ________________
0 1 0
_________________________________
0 1 1
_________________________________
1 0 0
_________________________________
1 0 1
_________________________________
1 1 0
_________________________________
1 1 1
_________________________________
ABC
F(A,B,C)
Your Circuit
Ref: Notes on breadboards and LEDs from http://www.proaxis.com/~iguanalabs/